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Full text of "The Cambridge Natural History"

CHAPTER VII
EUTHERIA----MARSUPIALIA
Order I,
THE Marsupials may be thus defined:—Terrestrial, arboreal, or
burrowing (rarely aquatic) mammals, with furry integuments;
palate generally somewhat imperfectly ossified; jugal bone reach-
ing as far as the glenoid cavity; angle of lower jaw nearly always
inflected. The clavicle is developed. Arising from the pubes are
well developed and ossified epipubic bones. Fourth toe usually
the most pronounced. Teeth often exceed the typical Eutherian
number of forty-four; molars generally four on each side of each
jaw. As a rule but one tooth of the milk set is functional, which
is (according to many) the fourth preniolar. Teats lying within
a pouch, in which the young are placed. Young born in an im-
perfect condition, and showing certain larval characters. There
is a shallow cloaca. The testes are extra-abdominal., but hang in
front of the penis. In the brain the cerebellum is completely
exposed; the hemispheres are furrowed, but the corpus callosum
is rudimentary. An allantoic placenta is rarely present
Structurally the Marsupials are somewhat intermediate be-
tween the Prototheria and the more typical Eutheria, with a
greater resemblance to the latter.
The name Marsupial indicates what is perhaps the most
salient character of this order. The pouch in which the young
are carried is almost universally present. It is less developed
1 Works dealing exclusively with the Marsupials are; Lydeklcer, in Allen's
Naturalists* Library, 1894 ; Aflalo, Natural History of Australia, Macmillan and
Co. 1896 ; Waterhouse, Natural History of Mammalia, i. London, 1848 ; Qld-
Md Thomas, British, Museum Catalogue ofMarsupialia and Monotremala, 1888,